1. Field of the Invention
The present invention relates to a seatbelt retractor for winding up an occupant restraining webbing used in a seatbelt system for protecting an occupant in a vehicle during emergency conditions, and particularly to a seatbelt retractor adapted to forcibly wind up the webbing to closely attach the same to the occupant during an emergency.
2. Description of the Prior Art
Since slack is formed between the webbing fastened to the occupant and the body of occupant during normal running condition of the vehicle, there is a possibility of imperfect restraining of the occupant occurring during an emergency until the occupant is moved because of the collision under an inertial force to eliminate the slack.
For the abovedescribed reason, there has been proposed a preloader mechanism in which, in an emergency of the vehicle, an explosive force of a powder is imparted to a takeup shaft to be rotated, whereby the webbing is rapidly wound up by the takeup shaft so that the webbing can be closely attached to the occupant, thereby improving the restraining performance of the webbing.
However, with this type of the preloader mechanism, the explosive force of the powder is high, and hence, the force acts on the occupant through the webbing as an oppressive force. As the result, the occupant, who has been violently moved in the direction of collision, is abruptly subjected to a restraining force in a reverse direction, thus possibly causing damage to the occupant.